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Old 2nd April 2007, 07:46 AM   #1
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Default Local Hamfest score!!!

On Saturday the Brampton area Hamfest was held at the arena about 45 minutes drive south of me (just NW of Toronto). I went last year and scored a very sweet sounding pair of vintage EV Model Four bookshelf speakers. This year I got lucky and found some items absolutely helpful towards my tube amp experimentation and crafting.

Items include a working Lambda variable regulated B+ power supply. Tube lineup includes a 5651 voltage reference tube, two 12AX7`s, six 6W6 pass tubes and two 5U4 rectifiers. This is great since I do not yet have a adjustable bench B+ supply beyond an ad hocked unit as needed comprising a variac, xfmer and rectifier plus caps and many clip leads.

A very new looking Heathkit capacitor checker with the brightest magic eye tube I have ever seen. Very cool and useful.

A large assortment of salvaged tube amp useable power xfmers, chokes, single ended tube TV and radio output xfmers and TV vertical sweep output iron (also useable as plate chokes).

A new Sylvania 6HV5 triode, Now I have four.

Some days it is still worthwhile getting up early!
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Old 2nd April 2007, 07:54 AM   #2
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Look at this beauty. Like new! Three bucks.
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Old 2nd April 2007, 08:26 AM   #3
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It is always nice to keep the hobby cheap. I always look at the local ebay, found lots of useful stuff...last acquisition were four 500VA transformers, with 2x115V primary and a secondary 0-200/500, with lots of taps in between.

Quote:
TV vertical sweep output iron
this sounds like iron that was produced by the millions and costs pennies nowadays - just like sweep tubes. Can you show us a picure, ant tell about your experience in using them as a plate load (achieved inductance, max current, DCR, etc)?

Erik
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Old 2nd April 2007, 08:56 AM   #4
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Quote:
Originally posted by ErikdeBest
It is always nice to keep the hobby cheap. I always look at the local ebay, found lots of useful stuff...last acquisition were four 500VA transformers, with 2x115V primary and a secondary 0-200/500, with lots of taps in between.



this sounds like iron that was produced by the millions and costs pennies nowadays - just like sweep tubes. Can you show us a picure, ant tell about your experience in using them as a plate load (achieved inductance, max current, DCR, etc)?

Erik

Gotta go back to my notes. Here is an image of the underchassis of my amplifier shown in my avatar. The gapped E-I lamination plate chokes for the parafeed and ultrapath connected 809 output triodes are matched vertical output iron from late 40`s RCA TV receivers. I recall about 400 ohms `ish for DCR and about 22 henries. They are happy at the 48 mA used in this amp. I used these because they were the only ones I had a matched pair of. I did not try to get more Z by wiring the low Z output winding in series. Being an output stage with lots of current I was worried about core saturation. I would do that no hesitation for a low level amp stage plate or grid choke. I have some singles in my TV salvage that measure up to 65 henries. I have hopes of finding more of use in the pile of vintage TV iron I just scored.

In my SET amp I have 620 VDC on the winding and the cores are grounded on these vintage RCA xfmers. That is way over their design spec based on the application. One showed some PD (partial discharge) very quiet occasional pop crackling in one channel when first put into service (I did not bake them first). Fortunately that went away in the first couple of days use. In almost a year the amp has been 100% trouble free.

When using salvaged output xfmers as plate chokes I identify the outer connection and believing it is subject to less parasitic capacitance put that side towards the tube anode for improved HF response. You can even use this trick with microwave oven transformers. Some of those will yield 20 or 22 henries on the HV winding and work great with low plate Z tubes like 6080`s.

You may read an account of my making this amplifier with pictures here.
SET amp from 1619 driving a 809. Opinion wanted.
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Old 2nd April 2007, 09:30 AM   #5
poynton is offline poynton  United Kingdom
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Location: A life on the ocean waves when I'm not at home in N. Wales (but I'm not Welsh so no sheep jokes!)
My local car boot sales usually turn up some goodies as do the local Freecycle groups.

Recent scores include a box of 'new' tubes - 813, E88CC, ECC83 and M8162 plus a load of others for £10 but Freecycle got me a Garrard401 and SME3009 for £0.00 - result!!!!!

Andy
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